| Since 1986,
photorefractive keratectomy has been used to reshape the cornea and
therefore changing its refractive power using an Excimer laser.
The center of the cornea has a thickness of approx. 0.5mm, and the
outer edges measure approximately 1.0 mm. The Excimer laser is used
to remove approximately 0.1 mm from the central corneal tissue thus
correcting the refractive error.
The PRK procedure is used for the correction of nearsightedness of up
to -6 diopter and astigmatism of up to 3 dioptres.
The disadvantages of PRK consist of the slow postsurgical healing process
and the sometimes very noticeable postsurgical pain.
The LASEK and Epi-LASIK method has been developed from the PRK procedure,
where structures of the corneal surface are ablated. To date, no scientific
studies have been made to investigate whether this new method leads
to the same problems during the healing process such as scarring and
regression (reappearance of the refractive error).
At the time, LASIK - laser ablation in the stromal bed of the cornea
without ablation on the corneal epithelium - became the method of choice
in order to avoid the aforementioned effects. Currently, LASIK is state-of-the-art.
If it is necessary to perform a PRK procedure today, it is done with
the LASEK or Epi-LASIK method.
With the LASEK method, the corneal epithelium (the outer corneal surface
of the eye) is separated with alcohol and rolled back, then the PRK
procedure is performed, afterwards the epithelium is rolled back and
covered with a therapeutic contact lens. Epi-LASIK uses a microkeratome
to remove the corneal epithelium.
There are less postoperative patient complaints - pain, vision fluctuations
- than compared to the older PRK method, in which the corneal epithelium
had been removed.
However, the LASEK and Epi-LASIKmethod are basically a PRK procedure.
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